This invention relates to scanning of surfaces in order to locate faults on the surfaces.
In a number of such scanning methods a beam of radiant energy is deflected by a rotating mirror polygon on to the surface to be scanned. The angle at which the beam strikes the surface can be chosen to suit the differing requirements of scanning systems in which the surfaces are inspected by reflection or by transmission. The amount of radiant energy reflected or transmitted by the surface is monitored by electronic means, for example a photocell, and any change noted, such changes indicating faults on the surface being scanned. Examples of surfaces which can be scanned are webs of film material and in particular coated webs of photographic film material.